The achievement "Frequent Flyer" is earned on the country - USA - Level 5 - Nothing But Air. This achievement is gained towards the end of the level, so familiarize yourself with this level before attempting to go for this achievement, as it can be quite tricky. As you progress throughout this level you will come to 5 hammers which smash down onto rotating flooring, pass this obstacle and you will come to a single fan which progresses onto several more fans. Pass over the single fan and once in mid air immediately pull down on the to go underneath the raised flooring and over the many more fans. From here on, just glide over the fans moving left and right with the until the achievement unlocks.